title: Association of third-trimester abdominal circumference with provider-initiated preterm delivery.
abstract: OBJECTIVE
  Evaluate the association of a small third-trimester abdominal circumference (AC < 10th percentile) in the setting of a normal estimated fetal weight (EFW ≥ 10th percentile) with gestational age at delivery, indication for delivery and neonatal outcomes.
  
  
  METHODS
  Retrospective cohort study at an academic hospital of women with singleton pregnancy seen for ultrasound from 28+0-33+6 weeks of gestation during 2009-2011. Outcomes were compared between two groups: normal AC (AC and EFW ≥ 10th percentile) and small AC (AC < 10th percentile and EFW ≥ 10th percentile).
  
  
  RESULTS
  Among 592 pregnancies, fetuses in the small AC group (n = 55) experienced a higher incidence of overall preterm delivery (RR: 2.2, 95% CI: 1.3-3.7) and provider-initiated preterm delivery (RR: 3.7, CI: 1.8-7.5) compared to those in the normal AC group (n = 537). Neonates in the small AC group had a lower median birth weight whether delivered at term (p < 0.001) or preterm (p = 0.04), but were not more likely to experience intensive care unit admission or respiratory distress syndrome (all p ≥ 0.35).
  
  
  CONCLUSIONS
  Small AC, even in the setting of an EFW ≥ 10th percentile, was associated with a higher incidence of overall and provider-initiated preterm delivery despite similar neonatal outcomes. Further investigation is warranted to determine whether these preterm deliveries could be prevented.
authors.affiliation: Department of Obstetrics and Gynecology, Northwestern University , Chicago, IL , USA .
authors.forename: Leah K
authors.initials: LK
authors.lastname: Hawkins
authors.forename: William T
authors.initials: WT
authors.lastname: Schnettler
authors.forename: Anna M
authors.initials: AM
authors.lastname: Modest
authors.forename: Michele R
authors.initials: MR
authors.lastname: Hacker
authors.forename: Diana
authors.initials: D
authors.lastname: Rodriguez
mesh_terms: D000005:Abdomen / Q000033:anatomy & histology*; D000328:Adult; D003657:Decision Making; D036861:Delivery, Obstetric / Q000379:methods* / Q000706:statistics & numerical data; D005260:Female; D005317:Fetal Growth Retardation / Q000175:diagnosis / Q000453:epidemiology / Q000628:therapy; D020567:Fetal Weight; D006282:Health Personnel; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology; D011263:Pregnancy Trimester, Third; D047928:Premature Birth / Q000453:epidemiology; D012189:Retrospective Studies; D064346:Sagittal Abdominal Diameter; D055105:Waist Circumference
keywords: Abdominal circumference; fetal surveillance; obstetrics; preterm delivery; third-trimester ultrasound